1. Field of the Invention
The present invention generally relates to compositions and methods for in vitro culturing of mammalian embryos and for enhancing achievement of pregnancy after implantation of the cultured embryo in the uterus of a suitable mammalian host. More particularly, the invention pertains to such composition and methods which employ a prostaglandin or prostaglandin analog for enhancing blastocyst quality and improving implantation potential of a treated embryo.
2. Description of the Related Art
The environment within the oviduct enhances the fertilization potential of sperm and promotes the development of cleaving embryos. Embryos co-cultured with oviductal epithelial cells have been shown to have improved development, hatching and implantation [Xu, 2001; Xu, 2000]. Prostacyclin (PGI2) is traditionally thought to be involved in maintaining blood and vascular homeostasis. However, recent observations in gene knock out mice suggest that it may have other physiological functions. The importance of endometrium-derived PGI2 is underscored by the observations made in the cyclooxygenase (COX)-2 knockout mice [Lim, 1997]. The endometrium of the COX-2 knock out mice failed to decidualize normally. As a result, transferred wild type embryos could not implant in the female mice deficient in COX-2. The aforementioned abnormalities could be, to some extent, corrected by administration of an exogenous PGI2 analog to the mother [Lim, 1999].
The role of oviduct-derived PGI2 in the development of pre-implantation embryos is not clear, because the litter size of PGI2 receptor (IP) knockout mice has not been compared with that of the wild type [Murata, 1997]. However, the genotypic distribution of pups arising from mating heterozygous IP knockout mice failed to conform to Mendel's Law: the prevalence of male and female pups with homozygous IP knockout genotype were 37% and 20%, respectively, less than expected [Murata, 1997].